LISBON, Portugal — The agency that sets the Internet addressing guidelines influencing how people navigate the Web defeated a proposal Friday to give adult Web sites their own “.xxx” domain.

Many in the adult-entertainment industry and religious groups alike had criticized the plan, which the Canadian government also warned this week could leave the Internet Corporation for Assigned Names and Numbers in the tricky business of content regulation.

The 9-5 decision by ICANN’s board came nearly seven years after the proposal was first floated by ICM Registry LLC. It was the third time ICANN has rejected such a bid. One member abstained from voting.

“We are extremely disappointed by the boards action today,” said Stuart Lawley, ICM’s president and chief executive. “It is not supportable for any of the reasons articulated by the board, ignores the rules ICANN itself adopted for the RFP, and makes a mockery of ICANN by-laws’ prohibition of unjustifiable discriminatory treatment.”

He added that ICM would pursue the matter energetically.
Many of the board members said they were concerned about the possibility that ICANN could find itself in the content regulation business if the domain name was approved. Others criticized that, saying ICANN should not block new domains over fears like that, noting that local, state and national laws could be used to decide what is pornographic and what is not.

Other board members said they believed that opposition to the domain by the adult industry, including Web masters, content providers and others, was proof that the issue was divisive and that “.xxx” was not a welcome domain.